1. Field of the Invention
The present invention relates to an electric vehicle mounted with an engine activated generator, and more particularly to a control method and apparatus of its engine.
2.
Description of the Related Arts
An electric vehicle is a vehicle driven by an electric motor. In the electric vehicle, the motor is rotated by means of an electric power supplied from a battery mounted on the vehicle and generates a driving force of the vehicle. As a power source of the motor, in addition to the battery mounted on the vehicle, a so-called engine activated generator can be used.
The engine activated generator is an apparatus comprising an engine and a generator mechanically driven by the output of the engine. The output power of the generator is used for driving the motor and for other purposes such as charging the battery. As described above, in the electric vehicle, the power is supplied from the engine activated generator to the motor to drive the vehicle, and such an electric vehicle is called a series hybrid vehicle (SHV).
The electric vehicle is a low environmental pollution vehicle in comparison with a vehicle driven by only an internal combustion engine such as a gasoline engine. That is, an electric vehicle mounted with no engine basically discharges no exhaust gas and, though the SHV is the electric vehicle mounted with the engine, the SHV operates the engine less frequently than the gasoline engine vehicle and thus discharges less exhaust gas.
For example, the SHV can be used as means for extending a running range of an electric vehicle having these advantages, that is, a range extender. When the vehicle is run by supplying the power to the motor from only the battery mounted on the vehicle, the battery is discharged and the state of charge (SOC) is dropped. The remarkable drop of the SOC shortens a life of the battery and hence usually the battery is charged at a proper frequency by using a suitable means. In an electric vehicle having no engine activated generator, it is required to carry out the charging by using an off-board charger. However, in an electric vehicle having an engine activated generator, the charging of the battery can be performed by using the output power of the engine activated generator in addition to using the off-board charger. Hence, in the case of the vehicle such as the SHV, the driving of the vehicle can be continued without executing the charging operation by the off-board charger.
For example, a conventional battery charging means using an engine activated generator mounted on an electric vehicle has been proposed, as disclosed in Japanese Patent Laid-Open No. Sho 55-157901. In this case, in response to a detection of the drop of the SOC of the battery, the engine activated generator is driven for charging the battery, and, when the battery is fully charged (SOC=100%) as a result of the charging, the engine activated generator is stopped. As disclosed in this document, conventionally, it is possible to use the engine activated generator as the charging means of the battery.
However, when the electric vehicle having the engine activated generator is driven, the engine activated generator may not be activated for a long time according to the preference or intention of a driver. That is, when the driver frequently carries out the battery charging by using the off-board charger so as to always keep the SOC of the battery in a good state, the frequency of operation of the engine activated generator can be reduced. For instance, when the battery charging by using the external power is lower in cost than the driving of the engine activated generator, there is a high motive for carrying out the charging by the external charger. Further, a driver having a firm faith in restricting production of the exhaust gas does not mind taking the trouble to do such a frequent battery charging operation.
When the engine activated generator is often not operated for a long time, a large a amount of fuel vapor is produced in an engine constituting the engine activated generator. For example, in an gasoline engine, a large quantity of gasoline vapor is caused in a gasoline tank. When the amount of vapor exceed an amount which is catchable by a charcoal canister, this vapor will be discharged to the atmosphere and this is counter productive to the primary purpose of the electric vehicle, namely realizing a low environmental pollution.